Flood Protection Information

Flooding in The City of Lewisville occurs primarily around the creeks that run through the city to the Elm Fork of the Trinity River. The river's water level is controlled by the Army Corps of Engineers through the Lake Lewisville Dam. Unless there is a severe flooding event, the lake and river will remain in their banks. Even if the lake and river are well within their banks, smaller creeks can flood with heavy rains. The main creeks affecting Lewisville are Timber Creek, Prairie Creek and Denton Creek on the west side of the city and Midway Branch and Indian Creek on the east side. In addition, all of these creeks have smaller tributaries subject to flooding. The Timber Creek Acres subdivision, located along Timber Creek, has had many flooding problems over the years. Owners with property near one of these flooding sources whether in the 100-year floodplain or not, should take precautions from flooding. Even if property has not flooded previously or recently it can still be flooded in the future due to changes in weather patterns and stream characteristics or a rain event that exceeds a 100-year storm. A 100-year storm does not mean that it will only occur only once each 100 years, but that there is a 1% chance in any given year that a storm that large will occur.

Flood hazards are mapped by the Federal Emergency Management Agency. The Flood Insurance Rate Maps (FIRM's) for the City of Lewisville along with other publications on flood protection and local flood studies can be found in the Engineering Department, located on the second floor of City Hall, 151 W. Church Street. You can visit the Engineering offices or call 972.219.3490 for information with regard to any questions you have about the flood hazard for your property and if requested, the engineering staff will visit your property to review flood problems and explain what can be done to improve the drainage for your property and neighborhood.

Emergency Preparedness and Emergency Warning

The City of Lewisville has prepared a Comprehensive Emergency Management Plan, and this plan meets the “Advanced Level” Planning Preparedness Status as prescribed in the Preparedness Standards for Emergency Management in Texas (TDEM-100) document. This Plan provides a framework for our City response to disaster, such as those caused by tornadoes, flooding or other hazard. City of Lewisville staff constantly train, exercise and practice the elements of this Plan.

Furthermore, the City of Lewisville employs a comprehensive emergency warning program, and has access to multiple tools that are used to notify the public of emergencies or disasters. During times of severe weather or potential floods, City officials are closely monitoring forecasts and are in close coordination with the officials at the National Weather Service, U.S. Army Corps of Engineers, broadcast meteorologists, storm spotters and other area jurisdictions. Additionally, City public safety crews and field personnel are monitoring real-time conditions around the City. If danger emerges, City officials will activate various warning systems, such as our Outdoor Warning System sirens and the Lewisville Citizen Alert emergency notification system, to ensure our residents and visitors are adequately notified of the danger. However, it is important to note that no single tool will provide enough warning to all residents in all situations – it is important that YOU have multiple ways of receiving emergency warnings.

Standard homeowners’ insurance policies do not cover losses due to floods. Because Lewisville is a participant in the National Flood Insurance Program, it is possible for property owners to obtain federally backed flood insurance. This insurance is available to any owner of insurable property in Lewisville, regardless of whether or not the property is located in a floodplain. It’s also important to know that basic flood insurance does not cover loss of contents. Loss of Contents due to flooding is a separate coverage that is also available to all property owners in Lewisville. If you have specific questions about flood insurance, contact your insurance agent for more information on rates and coverage. Insurance information is also available through FloodSmart.gov.

Flood Safety

If there is threat of a flood, there are several precautions property owners can take to decrease the risk of personal or family injury:

Do not walk or drive through a flooded area. It only takes a foot of flowing water to knock an adult off their feet, and less than 2 feet of flowing water to move a vehicle.

Keep children from playing in ditches, culverts and around storm drains.

Cut off all electric circuits at the fuse panel or disconnect all switches. Turn off and unplug all appliances. Shut off all water and gas services to your home.

Do not drive through a flooded area or around road barriers. The road or bridge may be washed out and it takes less than a two foot depth of flowing water to move a vehicle. Larger vehicles are not less susceptible to being carried away by moving water as there is more surface area for water to exert its force. More people drown in their cars than anywhere else.

Stay away from all fallen power lines and electrical wires. Electrocution is the second greatest cause of death due to flooding.

Property Protection - Home Improvements

There are measures you can take to protect your building from flood damage. One way to keep water away from your building is to grade your lot so water flows away from or around the foundation. In addition, earthen berms or small swales can be used to direct water away from a structure. You can also flood proof your building by making the wall and floors waterproof, with watertight closures for the doors and low windows. Elevating a building so it is above the flood elevation, especially if it is of pier & beam construction is another effective measure against flooding. In some cases this may mean raising your building by several feet. Also, keep materials such as sandbags, plastic sheeting, plywood and lumber handy for emergencies, to help minimize the damage when flooding does occur. You can also request sandbags from the Public Services Department in times of emergency by calling 972.219.3510.

Please note that before you build on, alter, regrade or fill on your property, you will need to check with the Engineering Division (Mr. Jeff Kelly, P.E., Assistant City Engineer phone: 972.219.3492) and Neighborhood Services (Mr. George Babineaux, Assistant Building Official phone: 972.219.3472) to determine whether a permit is required. The City of Lewisville requires permits for most property grading and filling and building improvements and construction. Consulting with a professional engineer is also advisable to ensure that your project will not increase flooding elsewhere. If you see any questionable dumping, filling or regrading work please contact Mr. Kelly. Projects without an engineering analysis and/or a permit may be illegal and could cause a greater flooding risk to your property. Please be aware that any property improvements that take place within a Zone A or AE floodplain require a Floodplain Development Permit in addition to normal building permits or grading permits.

New construction in the floodplain must have the finished floor elevation (bottom floor) two feet above the 100-year flood levels. If the cost of reconstruction, rehabilitation, addition or other remodeling improvements to a building exceeds 50% of the building’s original market value, then the entire building must meet the same construction requirements as a new building. This means that if your building is located in a flood zone and is damaged by any means, such as a fire, tornado, or by flooding, and you have repairs costing more than 50% of the value of the building, you must elevate or flood proof your building two feet above the base flood level. Other construction requirements, such as flood resistant materials and utility equipment resistant to flood damage, may also be required. All manufactured homes located in a floodplain must be elevated on a permanent foundation and anchored to resist flotation, collapse or movement. No new construction regardless of how small or insignificant it may seem is allowed in the floodway portion of the floodplain without significant review and in some cases an engineering analysis. In some cases, the construction may not be able to be permitted at all. The floodway is defined as the channel of a river or drainage way and the portion of the floodplain adjacent to the banks that carries most of the base flood. If your building is located in a floodway and is more than 50% damaged, you will not be able to rebuild. To see if your building is in the floodway, check with the Engineering Division at City Hall. In addition, any building construction or substantial improvements to a building (construction/improvement cost equals 50% or more of the value of the building) permitted in the floodplain must be followed up with an elevation certificate or flood proofing certificate filled out and sealed by a registered surveyor or engineer before the building or improved structure may be occupied. The City Building Inspections Division will also require a form board survey to ensure adequate elevations before the foundation is constructed.

The City of Lewisville Engineering Division (972.219.3490) and Building Inspections Division (972.219.3470) can answer many questions you might have related to construction of new structures, repairing existing structures and the building permit process.

Drainage System Maintenance and Protection

Another cause of flooding is due to drainage system blockages due to natural occurrences or illegal dumping in streams and ditches. Inlets and storm drains also need to be cleared to prevent water back up. A blocked channel cannot carry the amount of water required during a heavy rain, so consequently flooding occurs. The Public Services Department drainage maintenance program includes inspection of all public drainage systems twice a year and response to complaints if a public storm drain or public channel needs to be cleared. If your private property is next to a ditch or stream, please help keep the banks clear of brush and debris. Do not dump or blow your grass clippings, leaves or other debris into a ditch, creek, storm drain or street. Do not dump oil, grease, pesticides or other pollutants down storm drains, ditches or creeks. In the event of a storm emergency, if you have downed trees or other major blockages that are threatening your home or physical safety and need help with clearing call the Public Services Department at 972.219.3510. For privately owned drainage systems, routine clearing and maintenance are the responsibility of the property owner.

Do not dump oil, grease, pesticides or other pollutants down storm drains, ditches or creeks because it will damage the water quality and destroy the natural habitat of fish and wildlife. To help to properly dispose of household hazardous and electronic waste the City provides a free Household Hazardous Waste and Electronics Waste Program every 2nd Saturday of each month at the City Residential Convenience Center at 330 West Jones Street from 9 a.m. – noon. For more information contact the Public Services Department at 972.219.3504.

If you see any illegal dumping into streams, ditches, and storm inlets, please contact the Public Services Department at 972.219.3510.

Natural and Beneficial Functions of Flood Plains

In natural or undeveloped settings, a flood causes little or no damage. Floodplains in natural areas help reduce flood damage by allowing the water to spread over a large area, which reduces flood velocities and provides flood storage to reduce peak flows downstream. One way the city is trying to maintain natural conditions and reduce flood damage to property is by placing parks and open spaces in and around the floodways. Many city parks are located along the city's creeks and drainage ways, such as Central Park along Timber Creek, Leonard L. Woods Park along Prairie Creek and Raldon-Lake Cities Park along Fox Creek, Vista Ridge Park along Denton Creek, Lake Park Athletic Complex along Lake Lewisville and Lone Star Toyota of Lewisville Railroad Park along the Elm Fork of the Trinity River.